SIG M17 vs M18: Which One Should You Buy? (The Three-Second Answer)

Short answer: If you are going to carry it, buy the M18 — 3.9" barrel, 7.2" overall. If you want the longer sight radius for range work and competition, buy the M17 — 4.7" barrel, 8.0" overall. That is the whole decision, because mechanically only three parts separate the two pistols: the slide, the barrel, and the recoil spring assembly. Everything else is the same gun — same Fire Control Unit (FCU), same grip height and width, and the 17-round standard magazines are fully interchangeable, as are the 21-round extended magazines.